The present invention generally relates to mismatch calibration of a capacitive differential isolator.
Demands for low power, high speed isolated communication call for innovations in the architecture of communication channels. The use of capacitors as galvanic isolation barriers may play a leading role in improving performance, reducing form factor, and reducing costs of communication channels.
Capacitors are not inherently differential devices although they find application in differentially-driven isolator systems. Thus, to isolate a transmitter from a receiver, and to transmit a differential signal from the transmitter to the receiver, a capacitive differential isolator requires at least two capacitors.
It is desirable for a capacitive differential isolator to maintain noise and interference immunity when transmitting a differential signal from the transmitter to the receiver. If there is an impedance mismatch between the differential paths of the capacitive differential isolator, the immunity performance and the signal integrity along the capacitive isolation barrier get significantly degraded. Common-mode interferences are converted to unintended differential signals due to the impedance mismatch. These unintended differential signals cannot be distinguished from the intended differential signal and thus cannot be filtered out. Consequently, both the intended and unintended differential signals get transmitted to the receiver.
Since impedance mismatches have significant negative impact on the performance of communication channels, the inventor recognized a need in the art for calibrating impedance mismatches in capacitive differential isolators.